#include<bits/stdc++.h>
using namespace std;

const double eps = 0.000001;

int main()
{
	auto fun = [](double x) {return pow(x, 5)-15*pow(x, 4)+85*pow(x, 3)-225*pow(x, 2)+274*x-121;}; 
	
	double l, r, mid;
	l = 1.5;
	r = 2.4;
	while(fabs(r - l) > eps)
	{
		mid = (l+r) / 2;
		double t = fun(mid);
		if(t == 0)
			break;
		else if(t > 0)
			l = mid;
		else if(t < 0)
			r = mid;
	}
	cout<<fixed<<setprecision(6)<<mid;
//	printf("%.6lf", mid);
	return 0;
}

